Abstract Youth homelessness is a significant and growing public health problem, with unhoused youth being particularly vulnerable to negative health outcomes. Connecting these youth to services improves outcomes, and many communities are making efforts to do so. Youth homelessness is a complex challenge. Some communities are addressing it by a collective impact approach which relies on five key elements: 1) a common agenda; 2) shared measurement; 3) mutually reinforcing activities; 4) continuous communication and 5) a backbone organization. Collective impact requires communities invest significant time and resources to establish and sustain this powerful approach. The goal for this project is to develop and evaluate a community-based step-by-step technology-enabled solution to help communities implement a collective impact approach to youth homelessness. MosaicVillage: A Youth-Informed Platform to Reduce Youth Homelessness Through Collective Impact will help communities (1) assess youth needs and community readiness to create an action plan and develop a common agenda, (2) implement real-time communication between homeless youth and service providers in the community, (3) facilitate continuous collaboration amongst stakeholders, (4) establish and digitally collect data to monitor performance and outcomes, and (5) visualize and share this information. The long-term goals of MosaicVillage are to reduce negative health outcomes for youth experiencing homelessness and to end youth homelessness. During Phase I, the project team will use human-centered design to develop a minimum viable product (MVP) that contains the Readiness Assessment and Planning Tools and associated training materials to begin collective impact implementation. Specifically, these tools will enable communities to: 1) identify potential stakeholders, 2) assess the specific needs of homeless youth, 3) evaluate the capacity of local service providers to deliver services to them, 4) determine a community?s readiness to undertake a collective impact approach, and 5) create an action plan based upon these initial assessments. The project team will assess the MVP for MosaicVillage to establish the product?s proof of concept and technical feasibility. We will develop the entire MosaicVillage product in Phase II and evaluate its efficacy using a quasi-experimental design with multiple communities where MosaicVillage has not been implemented previously. Specifically, we?ll measure the impact of the full program on the mental health and behaviors of youth experiencing homelessness.